Function route_for_absent 

pub(crate) async fn route_for_absent(
    state: &AppState,
    auth_via: ReactiveAuthVia,
    req: &InjectionRequest,
    resp: &InjectionResponse,
) -> AbsentRoute

Decide AbsentRoute for a target no tier found live. Holding here is the default for an agent defined in this channel, so messaging works without the relay; the relay overrides it only when it says another install of the account holds the agent’s lease. Anything the relay cannot answer plainly keeps the old order (relay first), so an older relay changes nothing.